Butadiene (1,3-butadiene, CH2═CH—CH═CH2, CAS 106-99-0) is a linear, conjugated 4-carbon hydrocarbon typically manufactured (along with other 4-carbon molecules) by steam cracking petroleum-based hydrocarbons. This process involves harsh conditions and high temperatures (at least about 850 C.). Other methods of butadiene production involve toxic and/or expensive catalysts, highly flammable and/or gaseous carbon sources, and high temperatures. Globally, several million tons of butadiene-containing polymers are produced annually. Butadiene can be polymerized to form polybutadiene, or reacted with hydrogen cyanide (prussic acid) in the presence of a nickel catalyst to form adiponitrile, a precursor to nylon. More commonly, however, butadiene is polymerized with other olefins to form copolymers such as acrylonitrile-butadiene-styrene (ABS), acrylonitrile-butadiene (ABR), or styrene-butadiene (SBR) copolymers.
The diminishing total reserve of petroleum and growing concerns about supply security and climate change have intensified interests to produce alternative renewable carbon sources to supplant oil-based carbon sources for fuels, thermoplastics, etc. The most common alternative renewable carbon source in use today is ethanol, which reached 6.5 billion gallons in production in the US in 2007. Ethanol fermented from starch or sugar feedstocks is commonly added as a component to gasoline to control combustion and increase the octane rating of the fuel. Ethanol can also be dehydrated to ethylene for polyolefin production.
Other approaches involve the utilization of naturally occurring fats and oils to produce bio-diesel, bio-naptha, or bio-propane. One approach, described in EP 5249689, involves removing the major part of the non-triglyceride and non-fatty acid components, thereby obtaining refined oils. The oils can be fractionated, alkyl-esters can be transformed into bio-diesel by a transesterification or into linear paraffins such as the bio-naphtha. Other approaches involve the transesterification of waste oil and fat triglycerides with a short chain alcohol such as methanol to form fatty acid methyl esters (FAME).
While these approaches have some promise, the supply of raw materials for production will become a challenge as demand increases, making a process that uses more abundant feedstocks, such as lignocellulose or other naturally occurring sugar sources, more attractive.
Recently, efforts have been made to develop new processes for producing advanced biofuels. For example, fermentation can be used to produce higher chain alcohols (C3-C5) which contain a high energy density, and are compatible with the current infrastructure as they are less hygroscopic. These alcohols (e.g., isopropanol, 1-propanol, 1-butanol, isobutanol, 3-methyl-1-butanol, 2-methyl-1-butanol, isopentenol) also can be dehydrated to alkenes, which can be esterified, hydrogenated, or polymerized to yield a variety of compounds that can be used as fuels, fuel additives, or other commodity chemicals.
While a wide variety of commercial products can be manufactured by fermentation processes, there remain many challenges for recovery and purification of useful chemicals. For example, WO/2011/075534 discloses steps of solvent extraction to purify isoprene. While this process appears to work, it is limited to aerobic fermentation byproducts, where isoprene or butadiene streams contain significant amounts of nitrogen and oxygen.
The methods and systems disclosed herein are optimized to isolate and/or purify byproducts produced using anaerobic fermentation processes. These may result in 1,3-biobutadiene gas compositions containing various amounts of impurities as part of the fermentation process (e.g., water vapor from the fermentation media, carbon dioxide as a respiration product, as well as other organic bio-byproducts such as propanol). The inventive process and systems herein have the advantage of utilizing compression and distillation steps under low temperatures. The invention is also applicable for other conjugated diolefins such as isoprene.